Hotrunners that are typically used in injection molding systems are coupled to a nozzle that is heated. The temperature of the melt material that flows through the body of the nozzle is assumed to be the same as or similar to the temperature of the body of the nozzle itself. The temperature of the body of the nozzle is typically measured using a thermocouple which typically comprises a pair of wires comprised of two different materials that are physically mated with each other at a terminal contact point at which point the mated wires generate an electrical signal that is indicative of the temperature of the surrounding material at that contact point of the two thermocouple wires. In a hotrunner system the terminal contact point of a thermocouple is typically placed in physical engagement or contact with a selected surface of the body of the nozzle or with a sheath or tube or other structure that is in thermally conductive contact with the body of the nozzle in order to attempt to obtain a measurement of the temperature of the melt material that is flowing through the nozzle body at the selected point or position of the nozzle body to be measured.
The accuracy of the temperature reading at the selected point on or along the nozzle body, or on or along the tube or other structure in thermal contact with the nozzle body, is not necessarily reflective of the actual temperature at the particular selected point because the terminal mating point of the thermocouple is in too close physical proximity to the heater device that is used to heat the nozzle (or the tube or other structure with which the nozzle is in contact). Such close proximity of the terminal mating point of the thermocouple with the device that is used to heat the nozzle body causes the thermocouple to read the temperature of the heating device itself or the tube or sheath or other structure that heating device is in thermal contact with, and not necessarily the temperature of the melt material that is flowing through the nozzle at the location at which the terminal mating point of the thermocouple is located. The temperature of the heating device itself, or the structure that the heating device is in contact with, overwhelms the material with which the terminal point of the thermocouple is in contact with and thus the thermocouple is measuring a higher temperature than the actual temperature of the body of the nozzle itself at the precise location of the terminal mating point of the thermocouple resulting in a colder than desired nozzle body temperature (which adversely influences the temperature of the melt flowing through the nozzle body).